Double half RF pulses for reduced sensitivity to eddy currents in UTE imaging

Abstract

A method for creating a magnetic resonance image of an object with at least a first species and a second species, wherein the first species has a first T 2 time and the second species has a second T 2 time longer than the first T 2 time is provided. An excitation with an ultra short echo time using a pulse is provided, comprising a first subpulse that creates a transverse magnetization component for the first species and the second species and a second subpulse that creates a transverse magnetization for the first species and substantially returns the second species to a longitudinal axis, wherein the transverse magnetization component substantially decays for the first species during an interval between the first subpulse and the second subpulse. At least one echo is read. A magnetic resonance image is created from the at least one echo.

1. A method for creating a magnetic resonance image of an object with at least a first species and a second species, wherein the first species has a first T 2  time and the second species has a second T 2  time longer than the first T 2  time, comprising:
 providing an excitation with an ultra short echo time using a pulse, comprising;
 a first subpulse that creates a transverse magnetization component for the first species and the second species; and 
 a second subpulse that creates a transverse magnetization for the first species and substantially returns the second species to a longitudinal axis, wherein the transverse magnetization component substantially decays for the first species during an interval between the first subpulse and the second subpulse; 
 
 reading at least one echo; and 
 creating a magnetic resonance image from the at least one echo. 
 
   
   
     2. The method, as recited in  claim 1 , wherein the first subpulse has a first peak of a first polarity and the second subpulse has a peak at a second polarity opposite the first polarity. 
   
   
     3. The method, as recited in  claim 2 , wherein the first peak and the second peak have a time difference that determines a signal level based on the first T 2  and the second T 2 . 
   
   
     4. The method as recited in  claim 3 , wherein the excitation provides a slice-selective gradient. 
   
   
     5. The method as recited in  claim 4 , wherein the created magnetic resonance image has suppression of the second species. 
   
   
     6. The method as recited in  claim 5 , wherein the excitation is an Inverted Double Half RF pulse. 
   
   
     7. The method, as recited in  claim 6 , wherein the first subpulse and the second subpulse form an Inverted Double Half RF pulse. 
   
   
     8. The method as recited in  claim 7 , wherein providing the excitation further comprises providing a shim, wherein the shim and the second polarity opposite the first polarity reduce eddy current distortion. 
   
   
     9. The method, as recited in  claim 8 , wherein the first subpulse is a 90° pulse, wherein the first subpulse flips the first species and the second species to the transverse plane and wherein the second subpulse flips the first species to the transverse plane and the second species to the longitudinal axis. 
   
   
     10. The method as recited in  claim 1 , wherein the excitation provides a slice-selective gradient. 
   
   
     11. The method as recited in  claim 1 , wherein the created magnetic resonance image has suppression of the second species. 
   
   
     12. The method as recited in  claim 1 , wherein the excitation is an Inverted Double Half RF pulse. 
   
   
     13. The method, as recited in  claim 6 , wherein the first subpulse and the second subpulse form an Inverted Double Half RF pulse. 
   
   
     14. The method as recited in  claim 1 , wherein the providing the excitation further comprises providing a shim, wherein the shim and the second polarity opposite the first polarity reduce eddy current distortion. 
   
   
     15. The method, as recited in  claim 1 , wherein the first subpulse is a 90° pulse, wherein the first subpulse flips the first species and the second species to the transverse plane and wherein the second subpulse flips the first species to the transverse plane and the second species to the longitudinal axis. 
   
   
     16. A magnetic resonance imaging apparatus, comprising:
 a magnetic resonance imaging excitation and detection system; and 
 a controller electrically connected to the magnetic resonance imaging excitation and detection system, comprising:
 a display; 
 at least one processor; and 
 computer readable media with computer readable code operable to be executed by the controller, comprising:
 computer readable code for providing an excitation with an ultra short echo time using a pulse, comprising;
 a first subpulse that creates a transverse magnetization component for the first species and the second species; and 
 a second subpulse that creates a transverse magnetization for the first species and substantially returns the second species to a longitudinal axis, wherein the transverse magnetization component substantially decays for the first species during an interval between the first subpulse and the second subpulse; 
 
 computer readable code for reading at least one echo; 
 computer readable code for creating an magnetic resonance image from the at least one echo; and 
 computer readable code for displaying the image on the display. 
 
 
 
   
   
     17. The apparatus, as recited in  claim 16 , wherein the first subpulse has a first peak of a first polarity and the second subpulse has a peak at a second polarity opposite the first polarity. 
   
   
     18. The apparatus, as recited in  claim 17 , wherein the first peak and the second peak have a time difference that determines a signal level based on the first T 2  and the second T 2 . 
   
   
     19. The apparatus, as recited in  claim 18 , wherein the first subpulse and the second subpulse form an Inverted Double Half RF pulse.